1. Field
This invention relates to the sealing of the accept head portion to the lower cone portion of a hydrocyclone and is particularly directed to an improved sealing structure for hydrocyclone constructed of a resinous material such as polyurethane.
2. State of the Art
Cyclone-type centrifugal separators are well known. They are widely used for separating a fluid suspension of solids into light and heavy fractions. When the suspending fluid is liquid, these devices are commonly called hydrocyclone.
Hydrocyclone are commonly used in connection with oil rigs as desanders, desilters and for the recovery of barite salvage.
A hydrocyclone typically includes an accept head which connects to a centrifugal pump to accept mud through a tangential opening. The mud or slurry thus assumes a whirling motion within the accept head. The accept head connects to the large end of a lower cone. The whirling stream of fluid progresses downward toward the small end or apex of the cone body. In the process, the larger heavier particles are thrown out toward the interior surface of the cone, and the finer lighter particles tend to remain as part of the fluid mass near the center of the cone. Eventually, the larger particles and a small amount of fluid move to the bottom of the cone and pass out the apex as underflow. The remainder of the fluid, which contains the smaller particles, reverses direction and passes back up through the center of the accept head as overflow or effluent.
Dynamically, the flow inside the lower cone comprises a downward spiral adjacent the interior surface of the lower cone, and an upward spiral about the central axis of the cone. These two countercurrent flows generate edy currents which result in turbulent flow conditions.
The dyanamic hydraulic conditions required for proper operation of a hydrocyclone often involve operation at elevated pressures; e.g., above about 40 psi. Often much higher pressures, typically in excess of about 70 psi, are experienced intermittently due to hydraulic surges within the system. Hydrocyclone currently available within the art characteristically leak around the sealing surface between the head section and lower cone section, particularly during surge conditions.
In the case of polyurethane hydrocyclone used in the drilling industry for desanding, desilting, degasing and other surface mud handling operations, a circumferential clamping band is the usual means employed for forcing the sealing surface of the head section against the sealing surface of the lower cone. Considerable mechanical force is applied through the clamp, but even so, leakage has remained a problem. Various configurations have been applied to the mating sealing surfaces of the head section and lower cone section to help alleviate the leakage problem. For example, some manufacturers have provided a circumferential recess at the top of the lower cone section which functions as a socket to receive a depending circumferential projection (plug) from the head section. The projection and socket cooperatively form a male/female connection which is held firmly engaged by the metal ring clamp. Some versions of this system have incorporated a mating tapered interface between the male and female portions. Although these structures have considerably improved the performance of the seal, they have not totally alleviated the leakage problem. Leakage still occurs during service, particularly during surge conditions.